Bio-fouling or biological fouling is the accumulation of microorganisms, plants, algae, and/or animals on surfaces. The variety among bio-fouling organisms is highly diverse and extends far beyond attachment of barnacles and seaweeds. According to some estimates, over 1800 species comprising over 4000 organisms are responsible for bio-fouling. Bio-fouling is divided into microfouling which includes biofilm formation and bacterial adhesion, and macrofouling which is the attachment of larger organisms. Due to the distinct chemistry and biology that determine what prevents them from settling, organisms are also classified as hard or soft fouling types. Calcareous (hard) fouling organisms include barnacles, encrusting bryozoans, mollusks, polychaete and other tube worms, and zebra mussels. Examples of non-calcareous (soft) fouling organisms are seaweed, hydroids, algae and biofilm “slime”. Together, these organisms form a fouling community.
In several circumstances bio-fouling creates substantial problems. Machinery stops working, water inlets get clogged, and heat exchangers suffer from reduced performance. Hence the topic of anti-fouling, i.e. the process of removing or preventing bio-fouling from forming, is well known. In industrial processes, bio-dispersants can be used to control bio-fouling. In less controlled environments, organisms are killed or repelled with coatings using biocides, thermal treatments or pulses of energy. Nontoxic mechanical strategies that prevent organisms from attaching include choosing a material or coating with a slippery surface, or creation of nanoscale surface topologies similar to the skin of sharks and dolphins which only offer poor anchor points.
Antifouling arrangements for cooling units that cool the engine fluid of a ship via seawater are known in the art. DE102008029464 relates to a sea box cooler comprising an antifouling system by means of regularly repeatable overheating. Hot water is separately supplied to the heat exchanger tubes so as to minimize the fouling propagation on the tubes.